Is it necessary to cycle on and off of every peptide? The answer may not be as simple as you think, and it depends on *why* the peptide is being used. The Rejuvenation and Youth with GHK Cu Peptide Treatment Dr. Ahmet zyigit GHK Cu (Copper Peptide) is a naturally occurring peptide in the body that binds with copper to support cell repair and renewal. As we age, our levels decrease and thats where supplementation or GHK Cu Peptide Therapy: The Definitive Clinical Guide to Gene Modulation, Protocols, and Efficacy